readme.dac960

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

the "-i 16384" option to increase the bytes per inode parameter thereby
reducing the file system metadata.  Finally, on systems that will only be run
with Linux 2.2 or later kernels it is beneficial to enable sparse superblocks
with the "-s 1" option.


		      DAC960 ANNOUNCEMENTS MAILING LIST

The DAC960 Announcements Mailing List provides a forum for informing Linux
users of new driver releases and other announcements regarding Linux support
for DAC960 PCI RAID Controllers.  To join the mailing list, send a message to
"[e-mail]" with the line "subscribe" in the
message body.


		CONTROLLER CONFIGURATION AND STATUS MONITORING

The DAC960 RAID controllers running firmware 4.06 or above include a Background
Initialization facility so that system downtime is minimized both for initial
installation and subsequent configuration of additional storage.  The BIOS
Configuration Utility (accessible via Alt-R during the BIOS initialization
sequence) is used to quickly configure the controller, and then the logical
drives that have been created are available for immediate use even while they
are still being initialized by the controller.  The primary need for online
configuration and status monitoring is then to avoid system downtime when disk
drives fail and must be replaced.  Mylex's online monitoring and configuration
utilities are being ported to Linux and will become available at some point in
the future.  Note that with a SAF-TE (SCSI Accessed Fault-Tolerant Enclosure)
enclosure, the controller is able to rebuild failed drives automatically as
soon as a drive replacement is made available.

The primary interfaces for controller configuration and status monitoring are
special files created in the /proc/rd/... hierarchy along with the normal
system console logging mechanism.  Whenever the system is operating, the DAC960
driver queries each controller for status information every 10 seconds, and
checks for additional conditions every 60 seconds.  The initial status of each
controller is always available for controller N in /proc/rd/cN/initial_status,
and the current status as of the last status monitoring query is available in
/proc/rd/cN/current_status.  In addition, status changes are also logged by the
driver to the system console and will appear in the log files maintained by
syslog.  The progress of asynchronous rebuild or consistency check operations
is also available in /proc/rd/cN/current_status, and progress messages are
logged to the system console at most every 60 seconds.

Starting with the 2.2.3/2.0.3 versions of the driver, the status information
available in /proc/rd/cN/initial_status and /proc/rd/cN/current_status has been
augmented to include the vendor, model, revision, and serial number (if
available) for each physical device found connected to the controller:

***** DAC960 RAID Driver Version 2.2.3 of 19 August 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <[e-mail]>
Configuring Mylex DAC960PRL PCI RAID Controller
  Firmware Version: 4.07-0-07, Channels: 1, Memory Size: 16MB
  PCI Bus: 1, Device: 4, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFE300000 mapped at 0xA0800000, IRQ Channel: 21
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  SAF-TE Enclosure Management Enabled
  Physical Devices:
    0:0  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68016775HA
         Disk Status: Online, 17928192 blocks
    0:1  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68004E53HA
         Disk Status: Online, 17928192 blocks
    0:2  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       13013935HA
         Disk Status: Online, 17928192 blocks
    0:3  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       13016897HA
         Disk Status: Online, 17928192 blocks
    0:4  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68019905HA
         Disk Status: Online, 17928192 blocks
    0:5  Vendor: IBM       Model: DRVS09D           Revision: 0270
         Serial Number:       68012753HA
         Disk Status: Online, 17928192 blocks
    0:6  Vendor: ESG-SHV   Model: SCA HSBP M6       Revision: 0.61
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 89640960 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

To simplify the monitoring process for custom software, the special file
/proc/rd/status returns "OK" when all DAC960 controllers in the system are
operating normally and no failures have occurred, or "ALERT" if any logical
drives are offline or critical or any non-standby physical drives are dead.

Configuration commands for controller N are available via the special file
/proc/rd/cN/user_command.  A human readable command can be written to this
special file to initiate a configuration operation, and the results of the
operation can then be read back from the special file in addition to being
logged to the system console.  The shell command sequence

  echo "<configuration-command>" > /proc/rd/c0/user_command
  cat /proc/rd/c0/user_command

is typically used to execute configuration commands.  The configuration
commands are:

  flush-cache

    The "flush-cache" command flushes the controller's cache.  The system
    automatically flushes the cache at shutdown or if the driver module is
    unloaded, so this command is only needed to be certain a write back cache
    is flushed to disk before the system is powered off by a command to a UPS.
    Note that the flush-cache command also stops an asynchronous rebuild or
    consistency check, so it should not be used except when the system is being
    halted.

  kill <channel>:<target-id>

    The "kill" command marks the physical drive <channel>:<target-id> as DEAD.
    This command is provided primarily for testing, and should not be used
    during normal system operation.

  make-online <channel>:<target-id>

    The "make-online" command changes the physical drive <channel>:<target-id>
    from status DEAD to status ONLINE.  In cases where multiple physical drives
    have been killed simultaneously, this command may be used to bring all but
    one of them back online, after which a rebuild to the final drive is
    necessary.

    Warning: make-online should only be used on a dead physical drive that is
    an active part of a drive group, never on a standby drive.  The command
    should never be used on a dead drive that is part of a critical logical
    drive; rebuild should be used if only a single drive is dead.

  make-standby <channel>:<target-id>

    The "make-standby" command changes physical drive <channel>:<target-id>
    from status DEAD to status STANDBY.  It should only be used in cases where
    a dead drive was replaced after an automatic rebuild was performed onto a
    standby drive.  It cannot be used to add a standby drive to the controller
    configuration if one was not created initially; the BIOS Configuration
    Utility must be used for that currently.

  rebuild <channel>:<target-id>

    The "rebuild" command initiates an asynchronous rebuild onto physical drive
    <channel>:<target-id>.  It should only be used when a dead drive has been
    replaced.

  check-consistency <logical-drive-number>

    The "check-consistency" command initiates an asynchronous consistency check
    of <logical-drive-number> with automatic restoration.  It can be used
    whenever it is desired to verify the consistency of the redundancy
    information.

  cancel-rebuild
  cancel-consistency-check

    The "cancel-rebuild" and "cancel-consistency-check" commands cancel any
    rebuild or consistency check operations previously initiated.


	       EXAMPLE I - DRIVE FAILURE WITHOUT A STANDBY DRIVE

The following annotated logs demonstrate the controller configuration and and
online status monitoring capabilities of the Linux DAC960 Driver.  The test
configuration comprises 6 1GB Quantum Atlas I disk drives on two channels of a
DAC960PJ controller.  The physical drives are configured into a single drive
group without a standby drive, and the drive group has been configured into two
logical drives, one RAID-5 and one RAID-6.  Note that these logs are from an
earlier version of the driver and the messages have changed somewhat with newer
releases, but the functionality remains similar.  First, here is the current
status of the RAID configuration:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
***** DAC960 RAID Driver Version 2.0.0 of 23 March 1999 *****
Copyright 1998-1999 by Leonard N. Zubkoff <[e-mail]>
Configuring Mylex DAC960PJ PCI RAID Controller
  Firmware Version: 4.06-0-08, Channels: 3, Memory Size: 8MB
  PCI Bus: 0, Device: 19, Function: 1, I/O Address: Unassigned
  PCI Address: 0xFD4FC000 mapped at 0x8807000, IRQ Channel: 9
  Controller Queue Depth: 128, Maximum Blocks per Command: 128
  Driver Queue Depth: 127, Maximum Scatter/Gather Segments: 33
  Stripe Size: 64KB, Segment Size: 8KB, BIOS Geometry: 255/63
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Online, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Online, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Online, 3305472 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

gwynedd:/u/lnz# cat /proc/rd/status
OK

The above messages indicate that everything is healthy, and /proc/rd/status
returns "OK" indicating that there are no problems with any DAC960 controller
in the system.  For demonstration purposes, while I/O is active Physical Drive
1:1 is now disconnected, simulating a drive failure.  The failure is noted by
the driver within 10 seconds of the controller's having detected it, and the
driver logs the following console status messages indicating that Logical
Drives 0 and 1 are now CRITICAL as a result of Physical Drive 1:1 being DEAD:

DAC960#0: Physical Drive 1:2 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:3 Error Log: Sense Key = 6, ASC = 29, ASCQ = 02
DAC960#0: Physical Drive 1:1 killed because of timeout on SCSI command
DAC960#0: Physical Drive 1:1 is now DEAD
DAC960#0: Logical Drive 0 (/dev/rd/c0d0) is now CRITICAL
DAC960#0: Logical Drive 1 (/dev/rd/c0d1) is now CRITICAL

The Sense Keys logged here are just Check Condition / Unit Attention conditions
arising from a SCSI bus reset that is forced by the controller during its error
recovery procedures.  Concurrently with the above, the driver status available
from /proc/rd also reflects the drive failure.  The status message in
/proc/rd/status has changed from "OK" to "ALERT":

gwynedd:/u/lnz# cat /proc/rd/status
ALERT

and /proc/rd/c0/current_status has been updated:

gwynedd:/u/lnz# cat /proc/rd/c0/current_status
  ...
  Physical Devices:
    0:1 - Disk: Online, 2201600 blocks
    0:2 - Disk: Online, 2201600 blocks
    0:3 - Disk: Online, 2201600 blocks
    1:1 - Disk: Dead, 2201600 blocks
    1:2 - Disk: Online, 2201600 blocks
    1:3 - Disk: Online, 2201600 blocks
  Logical Drives:
    /dev/rd/c0d0: RAID-5, Critical, 5498880 blocks, Write Thru
    /dev/rd/c0d1: RAID-6, Critical, 3305472 blocks, Write Thru
  No Rebuild or Consistency Check in Progress

Since there are no standby drives configured, the system can continue to access
the logical drives in a performance degraded mode until the failed drive is
replaced and a rebuild operation completed to restore the redundancy of the
logical drives.  Once Physical Drive 1:1 is replaced with a properly
functioning drive, or if the physical drive was killed without having failed
(e.g., due to electrical problems on the SCSI bus), the user can instruct the
controller to initiate a rebuild operation onto the newly replaced drive:

gwynedd:/u/lnz# echo "rebuild 1:1" > /proc/rd/c0/user_command
gwynedd:/u/lnz# cat /proc/rd/c0/user_command
Rebuild of Physical Drive 1:1 Initiated

The echo command instructs the controller to initiate an asynchronous rebuild
operation onto Physical Drive 1:1, and the status message that results from the
operation is then available for reading from /proc/rd/c0/user_command, as well
as being logged to the console by the driver.

Within 10 seconds of this command the driver logs the initiation of the